To simplify, this guide is meant only for those who have purchased and are ready to install double-doors. The installation of double-doors is expectedly similar to the installation of a single door. Instructions are as follows:
Before anything else, the doorjamb must be the first piece to be installed. Before tightening with any bolts, check to see if threshold is leveled with the ground. If not, level the threshold using wood shims to level the threshold. In most cases there are 4 lugs welded as part of the doorjamb itself, though some have been known to have 6 lugs instead. These lugs will almost always be bolted on the frame with the use of 3/8″ X 2 1⁄2″ or 2″ lag bolts (Full threaded bolts are preferred) . When installing the jamb, make sure to tighten the two top lugs on either side first in order to make it easy to adjust the jamb later, if necessary.
The next step requires carefully removing the windows. This is done by loosening the latches and pulling them open. If done properly, they will easily lift off of the hinge pins with no excessive force required.
After this, the next time requires making sure the brass washers for the hinges are properly installed. Before the actual doors are hung, the brass washer itself needs to be in its proper place on each of the hinge pins. Once they are in place, each door must be lifted and placed onto its respective hinge pins. Once hung, the sliding bolts on the door that is not being worked on can be used to hold the doors closed.
At this point, you have already checked the evenness of the placement of the jamb and the doors, yet minor adjustments may be required in order to ensure proper installation. The following steps will ensure this is done.
While the doors are in their closed position and while you are looking at the doors from the inside:
First, look to see whether both doors are in line with one another and meet properly at the center point. You can do this by making sure the tops and bottoms of both doors are equal and in line with one another. If you realize they are not even, the bottom of the doorjamb would need to be adjusted slightly, either to the left or to the right, so that the doors can line up as they are supposed to.
Next, look at the height of the doors from top to bottom and ensure they close evenly. If either the top of the bottom of the doors seems to touch the astragal upon closing the doors, it is a sign that the doorjamb needs to be slightly adjusted because it may be twisted or deformed. By shifting the proper lug inward or outward until the doors line up evenly at their tops and bottoms, this issue could be remedied.
Once all sides and angles of the doors line up properly, the lower lugs can then be tightened into place. Double-check the actual fitment of the doors one last time to make sure the pieces did not shift during the lug-tightening process.
The last step requires lifting the windows, putting them into place, and securing their latches closed.